rogue star

A star that has escaped the grav3itational
pull of its host galaxy and is moving freely in, or toward, the intergalactic
void. A star that has acquired a sufficiently high velocity to break
free from the galaxy in which it for3med is called a hypervelocity
star. Several such stars have been found in our own Milky Way Galaxy.

More generally, any star that is in an unusual location or state of
motion.